Transformers



May 26, 1959 K. c. BUGG 2,338,654

TRANSFORMERS Filed Feb. 2, 1953 2 Sheets-Sheet 1 INVENTOR.

BY 62249 C Edgy,

K. C. BUGG TRANSFORMERS May 26, 1959 2 Sheets$heet 2 Filed Feb. 2, 1953INVENTOR.

@rzq C 5 United Stati wn? TRANSFORMERS Kenly C. Bugg, Fort Wayne, Ind.,assignor to Kendiclr Manufacturing Company, Inc., Fort Wayne, Ind., acorporation of Indiana Application February 2, 1953, Serial No. 334,4508 Claims. (Cl. 336-221) This invention relates to a new and improvedtransformer construction and more particularly to iron core transformersin compact form.

More specifically the invention relates to transformers initially woundon cores generally toroidal in design, which cores are flexible ordeformable. Such trans- 2,888,654 Patented May 26, 1959 fare wound andmay be adjusted after winding.

formers, after winding, are deformed to render the transv former morecompact and also more rigid.

Iron core transformers have come into wide use in electronic circuitseven in the higher frequency range with the development of various typesof cores such as powdered iron cores having low hysteresis and eddycurrent losses at such frequencies. Since compact construction is anessential of many modern types of electronic construction, it isdesirable to provide coil types with a minimum external field and" alsowith a minimum pickup of energy from adjacent units in the circuit. A J

the winding and assembly it is impracticable to provide absolutelyuniform transformers on a commercial scale. Many present day circuitsrequire accuracy and uniformity within a tolerance of one percent orless. It has therefore been the practice to adjust the circuitsexternally of the transformer as, for example, by adding a seriesresistance which must itself be very accurate, thus increasing both thecost and the volume taken up by the equipment.

The usual type of transformer with multilayer coils is not onlydiflicult to adjust but difiicult to wind within reasonable tolerancesas to circuit constants. The several layers are not uniformly wound andalso each layer has a different turn radius which varies further if theturns are overlapped or scramble wound. The distributed capacity of sucha coil is another 'variable affecting the effective reactance of thetransformer coils in finalassembly. While a toroidal transformer iseflicient and avoids many of these difiiculties it is not generallypractical for the reason that such a transformer, as usuallyconstructed, has a large size relative to. other forms of transformersof equal circuit characteristics.

It is an object of the present invention to provide a s new and improvedcompact form of transformer and method of producing the same.

It is a further object to provide a transformer wound I as an opentoroid and thereafter compacted to reduce the space occupied and torender the transformer more rigid.

It is an additional object to provide a transformer of this character inwhich the reactance of. .theseveral It is also an object to provide atransformer having a continuous closed core which is flexible so that itmay be bent to form a compact assembly.

It is another object to provide a transformer having a continuous corewith windings thereon and compactly bent upon itself and held in ahousing with portions of the windings exposed for adjustment.

It is a further object to provide a construction of this character witha core of suflicient length so that the desired windings may be formedthereon without the requirement for a multiplicity of winding layers.

It is an additional object to provide a transformer construction whichis simple to wind, form and adjust and which is compact and rigid infinal form.

Other and further objects will appear as the description proceeds.

The transformer described herein may be wound by means of the apparatusdisclosed in my copending appli- Figure 2 is a section taken on line 2-2of Figure 1' on enlarged scale;

Figure 3 is a fragmentary plan view of a modified form of core;

Figure 4 is a section taken on line 4-4 of Figure 3 with a coil woundthereon;

Figure 5 is a fragmentary plan view showing coil ends with adjacentturns soldered together;

Figure 6 is a section taken on line 6-6 of Figure 5 on an enlargedscale;

Figure 7 is a plan view, on a reduced scale, of a transformer coiled ina casing;

Figure 8 is a view similar to Figure 7, but showing a transformer foldedin a casing;

Figure 9 is a view similar to Figure 1 showing a multiple coretransformer;

Figure 10 is a section, on an enlarged scale, taken on line 10-10 ofFigure 9;

Figure 11 is a view similar to Figure 1 showing a two layer windingtransformer;

Figure 12 is a fragmentary view showing a split core construction; and

Figure 13 is a cross section of Figure 11 taken on line 13-13.

Referring first to the construction of Figures 1 and 2, the toroidalcore 21 is formed of a single length of suitable ribbon of magneticmaterial wound upon itself in spiral form with adjacent convolutions inclose contact. This core is shown as covered with a layer of insulation22 which may be formed of any suitable material such as plastic orvarnish sprayed or brushed on or applied by dipping. It will be alsounderstood that the insulation may comprise tape wrapped around thetoroidal core or in some cases insulation of the entire core may beeliminated. In such case, the core ribbon will be insulated before it iswound and the cut ends may then be treated with an insulating coatingbefore or after the Winding. This ribbon of magnetic material may be aalternate form the ribbon may be of plastic with the powdered ironcarried by adhesive on the face of the ribbon. The important feature isthat the complete core beflexible or deformable. Iron ribbons may bemade sufficiently thin so that they are very flexible and are adequatelyflexible even when wound in toroids of a number of adjacent turns sothat they may be deformed as shown herein. By way ofexample, the ribbonmay be of the order 'of a thousandth of an inch thick. For some uses thecore need be only on the order of a quarter of an inch or less wide andthick. When such a core is originally formed as a toroid several inchesin diameter it may-be readily deformed as shown. The core may also bewound of very fine wire. Numerous plastic materials are also capable ofcarrying iron powder while remaining flexible and readily deformable.The insulating materials used may be selected from the numerousinsulating varnishes and plastics available which arereadily flexed. Thewindings which carry the current will normally comprise fine copper wireas is usual in transformers.

The primary winding 23 is shown in this case as extending aroundsubstantially 180 of the core while the secondary windings 25 and 27 areshown as each extending approximately A of the circumference of thetoroidal core. These windings are single layer windings. As shown in thesection of Figure 2, an insulating coating 29 is applied over the entireassembly after the windings are completed. This final coating may beeliminated in some cases and in other cases it will not be applied untillater in the process of assembling the transformer in its compact form.

The core shown in Figures 3 and 4 differs from that shown in Figures 1and 2 in that it consists of a spirally wound rod or wire 31, the endsof which are brought together and butt welded, as shown in 32 if thewire is of solid metal. As described in connection with the core ofFigures 1 and 2, this rod 31 may consist of a suitable plastic withpowdered iron embedded therein. As another alternate form, it mayconsist of a plastic filament with a surface coating of powdered iron.As shown in Figure 4, the transformer windings 34 are wound on the corewire 31 in the same manner as the winding on the construction of Figures1 and 2. In the form of construction shown in Figure 4, the wire 31 isshown as coated throughout with an insulating covering 36 which may takethe form of a plastic or other synthetic material or of enamel orvarnish applied in any usual manner.

Figures and 6 show a method of adjusting the relationship between theinductance of the several coils of the transformer after the transformerhas been wound. In this case the windings have been made on the longside, that is, each Winding to be adjusted is provided with a few moreturns than have been found to normally be necessary so that anyadjustment required can be made by shorting out turns. The winding 38 isshown as terminating in a lead wire 40, while the winding 42 is shown asterminating in a lead wire 44. These windings and terminals might be,for example, adjacent ends of secondaries, such as secondaries 25 and 27shown in Figure 1. The primary 23 maybe wound with a predeterminednumber of turns and to give a specific example, it may be desired toimpress 100 volts on the primary and to induce 50 volts in each of thetwo secondaries. The induced voltage in each secondary may then bemeasured and turns adjacent the leads 40 and 44 shorted until thesecondaries show voltages of exactly 50. This shorting may beaccomplished by scraping off some insulation from the wire of turnsadjacent to the lead wires as, for example, by the use of small V-shapedfiles. The wires are then shorted by small solder segments 47 and 48 asshown. It will be understood thatthe secondaries may be brought intoproper balance by removing turns of wire if desired.

The cores used in both forms of construction'shown are wound with thecoils while in the forms of toroids having relatively large openings, asshown in Figure 1, although they need not be maintained in circular formduring the winding. Such large openings greatly facilitate the windingof toroids on usual coil winding machines. A transformer of thisrelative size, however, is impractical for several reasons. Present dayelectronic apparatus is becoming more and more condensed in size andconsequently transformers as well as other components must be reduced in"size. Another important difficulty with a toroidal transformer, asshown in Figure l, is the fact that distortion or vibration or bendingof any kind will temporarily or permanently destroy the accurate balancebetween the voltages of the several windings. A toroid of this size andproportion is extremely diflicult to mount and maintain rigidly.

Figure 7 shows one form of compacting the toroid and rendering it rigidand relatively immovable. It will be understood that the cores shown inFigures 1 to 4 are flexible or readily deformable. The wound transformerof Figure 1 or the like is stretched to bring it to the form in which itcomprises two long generally parallel portions joined by short arcuateportions at each end. In a suitable jig, one end of the transformer islooped around a pin 50, as shown in Figure 7. A second pin 52 is locatedadjacent pin 50 and spaced therefrom by approximately the width of thecross section of the wound transformer, as shown in Figure 7. Thetransformer is then arcuately bent in spiral form so that it may befitted within a cylindrical or ring-shaped housing or holding member 54.

In the construction shown in Figure 7, a plurality of smaller pins 56are placed at intervals so as to maintain the transformer portionsspaced from each other and from the housing 54. All of these pins may beloosely placed in a suitable jig so that after the winding has beencompleted and the ring 54 put in place, the transformer maybe removedwith the pins 50, 52 and 56 held in placeby the transformer and housing.As an alternate form, the housing 54 may take the form of a cup with aclosed bottomand an open upper face and the pins 50, 52 and 56 may bepermanently secured in place in the cup. The pins 50, 52 and 56 willusually be formed of non-magnetic and non-conducting material.

The form'of construction shown in Figure 8 is similar to that shown inFigure 7 with the exception that instead of the transformer beingspirally wound, it is folded upon itselfaround the pins 57, 58, 59, 60and 61. It is then held in its formed position by the housing 63. Itwill be understood that the number of folds and number of pins may bevaried as desired. Here again the housing 63 may be a rectangularmember, open at the top and bottom, or it may have a closed bottomsupporting the pins; 57 to 61 inclusive.

In the forms of construction shown in Figures 7 and 8, the relativeinductance of the primary and secondaries may be and normally will beadjusted after the transformer has been distorted and compacted. Thiscan be accomplished by the method shown in Figures 5 and 6. It isalsopossible, due to the clearances afforded between turns by thespacing and holding pins, to remove turns from or to add turns to any ofthe windings as may be necessary after the transformer has beeninstalled in the housing. Should it be desired to remove or add turns,the housing is preferably in the form of a ring or frame rather than inthe form of a cup.

The form of construction shown in Figures 9 and 10 includes a pluralityof flexible cores 67 and 68 having the windings 69 and 71 wound uponthem respectively. A third winding 73 is shown as wound around the twocores 67 and 68 and their windings 69 and 71. Normally the windings 69and 71 will be secondaries while winding 73, is a primary. It will beapparent that the arc, covered by the various windings, may beproportioned so that portions of. both secondaries are exposed and notcovered by the primary. Thus it is possible to make suitable adjustmentof the inductance of the various windings after the windings have beenput in place.

The fonm of construction shown in Figure 11 differs from that shown inFigure 1 in that the secondaries 80, 81, 82, 83 and 84 are shown assuperposed over the primary winding 86. A portion of the primarywinding, however, is exposed so that its inductance may be adjustedassaesa as well as the inductance of any or all of the secondaries. Theform of construction shown in Figure 12 includes a core 90 which may beformed either of wire or flat tape as shown in Figures 2 or 4. A primarywinding 92 is shown as wound on the entire core for a portion on thecircular arc. The core is then divided and a secondary 94 is wound onone portion of the core while another secondary 96 is wound upon theremainder of the core. The core, being flexible, it will be apparentthat the core may be divided in this manner and separated suflicientiyto facilitate the winding of the two secondaries. After the secondariesare wound, the two portions 97 and 98 of the core may be broughttogether to bring the secondaries adjacent each other and to cause thetransformer to assume the general appearance of the toroids of Figures1, 9 and 11. It will be understood that the forms of construction shownin Figures 9 to 12 may also be deformed and compacted, as shown inFigures 7 and 8.

It will be apparent that the invention may take any one of a variety offorms as to core design and construction and as to the exact arrangementby means of which it may be compacted and held rigid in its final form.All forms, however, include a continuous toroidal core or cores. It willbe understood that the cross section of the toroid may be rectangular,as shown in Figure 2, or circular, as shown in Figure 4, or may takeother suitable shapes. After the transformer has been compacted as shownin Figures 7 and 8 or in any other suitable manner and has been adjustedfor use it may be embedded in any suitable plastic material or the likewhich will not adversely afiect its electrical characteristics. In thepreferred forms of construction, each winding comprises a single layerso that all coils may be uniformly spaced in commercial production toassure products having substantially uniform electrical characteristics.Where space and the electrical requirements will permit, the forms ofconstructions of Figures 1 to 4 inclusive are preferred. In theseconstructions all coils are of a single layer wound directly upon thecore.

It will be understood that the constructions shown are illustrative onlyand I contemplate such modifications as come within the spirit and scopeof the appended claims.

I claim:

1. A transformer comprising a continuous flexible magnetic corestructure and flexible primary and secondary current carrying windingson said core, said core having folds to form adjacent core portionslying in a common plane.

2. A transformer comprising a continuous flexible magnetic corestructure and flexible primary and secondary current carrying windingson said core, said core having folds to form adjacent core portionslying in a common plane and a housing fitted about the transformer toretain it rigidly in folded position.

3. A transformer comprising a flexible toroidal magnetic core andflexible primary and secondary current carrying windings on said core,the toroid having substantially parallel portions connected by arcuateportions, said core having folds to form a compact assembly.

4. A transformer comprising a flexible toroidal magnetic core andflexible primary and secondary current carrying windings on said core,the toroid having substantially parallel portions connected by arcuateportions, said core having folds to form a compact assembly, a housingto receive and hold said assembly and nonmagnetic spacers locatedbetween adjacent portions of the core.

5. A transformer comprising a flexible toroidal magnetic core andflexible primary and secondary current carrying windings on said core,the toroid having substantially parallel portions connected by arcuateportions, said core having folds to form a compact assembly and ahousing to receive and hold said assembly, the housing exposing endportions of each of said windings whereby the length of said windingsmay be adjusted after assembly.

6. A transformer comprising a flexible toroidal magnetic core andflexible primary and secondary current carrying windings on said core,the toroid having substantially parallel portions connected by arcuateportions, said core having folds to form a compact assembly, a housingto receive and hold said assembly and nonmagnetic spacers locatedbetween adjacent portions of the core, the housing and spacers beingformed to expose end portions of each of said windings whereby thelength of said windings may be adjusted after assembly.

7. A transformer comprising a flexible toroidal core, a single layerwound primary on said core, at least one secondary wound in single layerover the primary and exposing a portion of at least one end of theprimary winding, the core with the windings thereon having folds to formadjacent core portions lying in a common plane.

8 A transformer comprising a flexible divisible toroidal core, a portionof the core being divided into at least two portions, coils wound onsaid divided portions, at least one coil wound on the undivided portion,the core with the windings thereon having folds to form adjacent coreportions lying in a common plane.

References Cited in the file of this patent UNITED STATES PATENTS1,289,418 Elmen Dec. 31, 1918 1,339,793 Smith May 11, 1920 1,586,889Elmen June 1, 1926 1,965,649 Jaumann July 10, 1934 1,978,568 Crossley eta1. Oct. 30, 1934 2,267,955 Squibb Dec. 30, 1941 2,407,391 WoolfolkSept. 10, 1946 2,436,742 Bussey Feb. 24, 1948 2,542,806 Ford et a1. Feb.20, 1951

